Flashcards
ClinChem week 11- Method Selection and evaluation
Cards in this deck (24)
- 1FIRST STEP of method selections and evaluaiton?Confirm need; define goals -- a decision of lab administration with input from all laboratorians
- 2EVALUATING NEW METHODInvolves much testing and analysis, comparing old method to the one you want to get
- 3Practicality characteristicsFactors that determine whether the method/technology can actually be implemented
1) personnel skills required (how much training is required?)
2) equipment/space required
3) workload expected (how many tests can be done?)
4) special specimen or specimen handling
5) cost per test and reimbursement - 4Reliability characteristicsRelate specifically to method/technology performance; requires experimental studies and statistical analysis of results
1) precision
2) accuracy
3) analytical sensitivity and specificity
4) recovery and effects of interferences
5) linearity of range
6) reagent stability - 5Analytical rangeRange of concentrations in a specimen over which the method/technology works without modification
- assessed by using broad range of linearity standards
- range should be broad enough to include 95% of expected clinical specimens without dilution - 6Analytical sensitivitythe ability of a method/technology to detect small quantities of the measured component
- assessed using precision tests
-“detection limits” must be determined with range tests - 7Detection limitthe smallest single result that can be distinguished from a blank 95% of the time
-also related to precision
-depends on the amplitude of blank readings
-Specified by Physicians (pathologists) - 8Blank readingsresponses of the method/technology due to reagent and sample constituents without analyte being present
- measure reagent only
- measure sample with analyte removed with single reagent added
- if blank readings are high, it is okay as long as they are stable (consistently high) - 9Analytical specificityability of a method/technology to analyze only the analyte it is supposed to
- related to accuracy
- needs to be a lack of crossreactivity with related substances
- typical interfering substances must have no effect - 10Interferencerelated to specificity
The effect of some component on the accuracy of the result (hemolysis, lipemia, etc.)
- related to specificity - 11RecoveryAbility of a method to measure only pure analyte when you add that analyte to a routine sample
- related to specificity and accuracy - 12PrecisionAgreement between replicated (repeated) measurements of the same analyte
-Within-run
-Within-day
-Day-to-day - 13Outline of Evaluation Study1. Plan to do testing on days when workload is not heavy; plan with personnel in advance
2. Obtain necessary reagents, kits, information needed
3. Begin testing of patient samples; determine within-run precision
4. Determine analytical range
5. Recovery Determination
6. Interference Testing
7. Carryover interference Testing
8. Day-to-Day Precision Testing - 14Within-run precision testingUsing a sample with a known value (control or single sample), run it 10-20 times
- calculate SD (called SDobs)
- compare SDobs with allowable SD (SDa)
- SD should be small; observed SD should match allowable SD - 15Determine analytical rangeThe highest and lowest values the technology/method can detect
- determines method sensitivity and linearity by assessing standard samples or dilutions
- Look at standard curve - 16SensitivityThe lowest value that can be reliably determined without being a false positive
- 17LinearityRange over which patient results can be reported without dilution
- 18Standard Curvemust be set using standards that will encompass range docs will be using
- 19Recovery DeterminationThe ability of a technology/method to measure a known added amount of analyte to a sample.
- Analyze a set of samples that consists of baseline (known amount) samples and test samples (baseline + known amount of analyte); determine values
- % recovery = (amt recovered/amt added) X 100 - 20Interference TestingSimilar to recovery experiment, except an interfering substance is added to sample containing known amount of analyte
-Prepare baseline samples and test samples (contain interferant)
- determine difference in analyte concentration btw test and baseline
- No calculations here, just look at difference - 21Carryover Interference TestingIn equipment that utilizes automatic pipetting, must determine if a high level of analyte in one sample affects the sample that follows
-Prepare a run of high samples followed directly by low to normal samples (all values must be determined beforehand) - 22Day-to-day precision testingOver four week period (or at least 20 days), precision of technology/method must be tested
-Serum pools or control material can be used
-One run per day using same samples each time
-determine SD and mean and compare to allowable limits - 23ComparisonMethod comparison of new vs. old technology/method. Data analysis involved here.
- Old method = "reference"
- New method = "test" - 24Final Steps1) Determine reagent stability using different batches or lot numbers of kits
2) Establish new reference ranges
3) Prepare a report for management; document procedure by writing new procedure
4) Inform clinical staff about the new testing procedure
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- Lab Exam 2 Clinical Chemistry II Flashcards on ClinChem week 11- Method Selection and evaluation , created by Fritz Hull on 07/04/2016.
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- Fritz Hull
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